Radio apparatus

ABSTRACT

In a radio apparatus, the band of a loop filter of a synthesizer in a blank channel searching state is narrower than the band in a communicating state. In addition, a radio wave environment is measured. A characteristic necessary for the radio apparatus is determined corresponding to the measured radio wave environment. The power is controlled corresponding to the performance of the radio apparatus. Thus, the power consumption is decreased. In addition, the efficiency of the output power is improved. In the radio apparatus, the current consumption of a power amplifier PA is measured. A matching circuit (LNA or MIX) of the antenna is adjusted with the measured result so as to decrease an antenna loss. In the radio apparatus, a DC offset is removed from the transmitted power and the reflected wave. When the DC offset is removed using an AC coupling capacitor, the deterioration of the frequency characteristic of the receiving portion is compensated with a capacitor in a digital signal process. In the radio apparatus, a transmission power detecting portion is structured as an IC chip. The transmission power detecting portion detects the transmission power corresponding to leakage currents in the power supply of the IC chip and the ground. Thus, when the power is detected, a power loss is suppressed. Consequently, the power consumption of the radio apparatus can be decreased.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a radio apparatus such as aportable radiotelephone apparatus.

[0003] 2. Description of the Related Art

[0004] In recent years, an increasing number of portable radiotelephoneapparatuses (hereinafter referred to as portable telephone apparatuses)have been used. In addition, portable telephone apparatuses that aresmall and that have high performance have been aggressively developed.

[0005] Current developing trends of portable telephone apparatus are forexample small size for high portability, low power consumption for longtime operation, and high linearity for high resistance againstdisturbing waves.

[0006] Currently, studies for solving problems necessary to accomplishsuch features have been performed.

[0007] Next, problems of the current portable telephone apparatus willbe described in the order of a receiving portion, a synthesizer (namely,a local oscillator), a transmitting portion, and an antenna.

[0008] First, problems of the receiving portion will be described.

[0009] The receiving portion has two problems. As a first problem, thecurrent consumption of the portable telephone apparatus is large. As asecond problem, when a signal is received, a DC offset takes place,resulting in causing the reception characteristic of the portabletelephone apparatus to deteriorate.

[0010] Since the reception characteristic of the portable telephoneapparatus should always satisfy the required performance, the receptioncharacteristic is designated so that the portable telephone apparatusproperly operates in the worst radio wave environment. An example of theworst radio wave environment is a situation of which an unnecessarysignal defined as a mutual modulation characteristic or a selectivity ofadjacent channels is present. In other words, when an unnecessary signalother than a necessary signal is present in a system band, the level ofthe unnecessary signal is the maximum value of which a desired bit errorrate defined in the system is satisfied.

[0011] Generally, to satisfy the standard value of the system in theworst radio wave environment, the radio apparatus should properlyoperate in the worst condition. Thus, in other than the worst radio waveenvironment, the portable telephone apparatus operate with theperformance that satisfies the worst condition. To satisfy the standardin case of the worst radio wave environment, the receiving portion ofthe portable telephone apparatus should have linearity. In other words,the distortion of the receiving portion should be decreased so that thestandard is satisfied. This problem relates to currents that flow incircuit blocks of the receiving portion (such as a low noise amplifierand a frequency converter).

[0012] Generally, to improve the linearity of a circuit, the operatingcurrent thereof should be increased. Thus, the power consumption of theportable telephone apparatus considered for the worst radio waveenvironment excessively increases. This is because the portabletelephone apparatus is not always in the worst radio wave environment.In other words, the portable telephone apparatus normally operates inother than the worst radio wave environment.

[0013] Next, the second problem of the receiving portion (namely, when asignal is received, a DC offset causes the reception characteristic todeteriorate.

[0014] Generally, in an active circuit such as a frequency converter, alow frequency filter, or a low frequency amplifier used in the receivingportion of the portable telephone apparatus, the output signal thereofoverlaps with a desired signal, thereby generating a DC component. Sucha DC component is generated by a self-mixing operation.

[0015] As the simplest technique for removing the DC component, an ACcoupling capacitor may be connected to the output stage of the activecircuit. In this case, part of the desired signal component is deleted.In other words, a notch takes place.

[0016] Thus, a carrier-to-noise (C/N) characteristic may be improved foran FSK signal with a high modulation index of which a desired signalcomponent is small in the vicinity of the DC region.

[0017] A technique for removing a DC offset using an AC couplingcapacitor has been proposed. This technique can be effectively used fora two-value FSK signal with a high modulation index for pagers. Since asignal component in the vicinity of the DC region is small, the ACcoupling capacitor does not largely attenuate a signal component.

[0018] However, in an FSK signal and a four-value FSK signal that havebeen used for high speed data transmission in recent years and that havelow modulation indexes, since there are many signal components in thevicinity of the DC region, the second problem cannot be practicallysolved.

[0019] Such a DC offset that takes place in the receiving portion has aproblem in the heterodyne system. This problem is much serious in thedirect conversion system that has been used in the mobile communicationfield in recent years. The problem of the DC offset in the directconversion system has different features from the problem in theheterodyne system. Next, the features of the problem in the directconversion system will be described.

[0020] In the direct conversion system, an external radio signal (RFsignal) and a local signal with the same frequency thereof are sent to amixer so as to directly convert an RF signal into a baseband signal.

[0021] When the mixer is mathematically ideal, the isolation betweeneach terminal is infinite. Thus, a signal supplied to a particularterminal does not take place at other terminals.

[0022] However, since a mixer used in the direct conversion typeportable telephone apparatus does not have an infinite isolation, alocal signal of the portable telephone apparatus is radiated from theantenna. The local signal radiated from the antenna is reflected by anexternal reflector. The reflected signal is received by the antenna andthen sent to the mixer. Since the frequency of the signal that is sentto the mixer from the antenna is the same as the frequency of the localsignal, a multiplying operation as a mixing function causes a DCcomponent (namely, a DC offset) to take place at a baseband outputterminal.

[0023] Since the DC offset varies depending on the amount of reflectionof the local signal (namely, a reflector in the vicinity of theantenna), this DC offset more adversely affects the receptioncharacteristic than a DC offset of the portable telephone apparatus anda DC offset of an active device.

[0024] Since the direct conversion type portable telephone apparatus issmall, the user carries it with his/her hand, bag, and pocket, thesituation of an external reflector varies time by time. Thus, since theamount of reflection of a local signal varies time by time, the DCoffset varies time by time. Since the DC offset cannot be suppressed,the reception sensitivity deteriorates.

[0025] To compensate the DC offset, a capacitor may be disposed in adownstream circuit. Since the capacitance of the capacitor is constant,a time-varying transient response of the DC offset largely affects areception error rate.

[0026] Thus, the conventional receiving portion cannot solve the twoproblems with respect to the low current consumption and the improvementof the reception characteristic. In particular, the problems in thedirect conversion system are severer than the problems in the heterodynesystem. Next, the problem of the synthesizer of the conventionalportable telephone apparatus will be described.

[0027] In the conventional portable telephone apparatus, a frequencysynthesizer is used. The frequency synthesizer comprises a referenceoscillator, a reference frequency divider, a phase comparator, a loopfilter, a VCO, and a comparing frequency divider. The frequency of thecomparing frequency divider is varied from N1 to N2 so as to switch afrequency. The frequency switching time depends on a natural angularfrequency ωon and a dumping coefficient ζ of the loop of the loopfilter. When the natural angular frequency and dumping coefficient areselected for a stable oscillation frequency and low noise, the frequencyswitching time becomes long.

[0028] The frequency synthesizer of this type should have a lowphase-to-noise characteristic, the frequency switching time becomeslong. Thus, when the conventional frequency synthesizer is used for aTDMA type portable telephone apparatus, the apparatus cannot search ablank channel using a blank slot in the communicating state.

[0029] Next, the transmitting portion of the conventional portabletelephone apparatus will be described.

[0030] The transmitting portion of the conventional portable telephoneapparatus comprises a frequency converter, a variable attenuator, apower amplifier, a transmission power controlling circuit, atransmission/reception switch, a band pass filter, a directionalcoupler, and a power detector. The frequency converter, the variableattenuator, the power amplifier, the transmission power controllingcircuit, the transmission/reception switch, and so forth can be easilystructured as an IC device. Thus, the sizes of these structural partshave been decreased corresponding to the advancement of the ICtechnologies.

[0031] However, since it is difficult to structure the band pass filterand the directional coupler as an IC device, these parts should bemounted on a mother board.

[0032] For example, the directional coupler is a chip part with a sizeof 5 mm×5 mm. On the other hand, the power detector is structured as adiode switch having a diode, a capacitor, a resistor, and so forth. Dueto the mounting areas of the diode, capacitor, resistor, and so forth,the size of the power detector exceeds 5 mm×5 mm.

[0033] Thus, unlike with the requirement of the size reduction, thevolume of the portable telephone apparatus adversely increases. Inaddition, since the directional coupler wastes an output power, theoutput power of the power amplifier should be increased so as tocompensate the wasted power. Consequently, the power consumption of thetransmitting portion increases.

[0034] Next, the problems of the antenna of the conventional portabletelephone apparatus will be described.

[0035] To improve the portability of the portable telephone apparatus,the sizes of the battery and antenna have been remarkably decreased.However, the size of the circuit of the portable telephone apparatus hasnot been sufficiently decreased. Thus, considering the decrease of theoverall size of the portable telephone apparatus, the size of theantenna should be further decreased.

[0036] On the other hand, there are problems of the body of the useragainst the antenna. The body of the user absorbs or scatters a radiofrequency wave. In addition, the body causes the operating impedance ofthe antenna to vary. From a view point of a radio frequency, the bodyfunctions as a radio wave absorber with a high dielectric constant.Thus, the body of the user causes the radiation characteristic of theantenna to deteriorate.

[0037] Since the size and thickness of the portable telephone apparatushave been decreased, the ear of the user tend to further approach to theantenna, resulting in causing the antenna characteristic to furtherdeteriorate.

[0038] As one of factors of such a deterioration, the body of the usercauses the impedance of the antenna to fluctuate. This situation will bedescribed assuming that the antenna is used for transmitting a signal.

[0039] To cause the antenna to radiate a radio wave, a power should besupplied to the antenna. The optimum condition-of the power supplied tothe antenna is in that the impedance of the feeder line is equal to theimpedance of the antenna. When the impedance of the antenna fluctuatesfrom its optimum value, a power on the feeder line is reflected at theinput edge of the antenna to the transmitting amplifier. This reflectionsometimes causes the amplifier to oscillate.

[0040] Next, a technique that can solve such problems and that can beeasily analogized and problems involved in the technique will bedescribed.

[0041] To suppress the power from being reflected at the input edge ofthe antenna, the frequency band of the antenna is widened. In otherwords, even if the input impedance fluctuates due to the approaching ofthe body of the user, the fluctuation of the wide frequency band antennais smaller than that of a narrow frequency band antenna. However, whenthe frequency band of the antenna is widened, the volume of the antennashould be increased. Thus, the technique for widening the frequency bandof the antenna contradicts with the decrease of the size of the portabletelephone apparatus.

[0042] As another technique for suppressing the reflection of the powerat the input edge of the antenna, the impedance of the antenna isadjusted in such a manner that when the body of the user approaches theportable telephone apparatus the impedance becomes optimum. However, itcannot be said that this technique is not unconditionally good. This isbecause the portable telephone apparatus is not always used in the statethat the body of the user approaches the portable telephone apparatus.Since the user carries the portable telephone apparatus with his/herhand or bag, the operation state thereof varies time by time. Thus, theamount of fluctuation of the impedance of the antenna variescorresponding to the operation state of the portable telephoneapparatus. This is because the substance and distance of the body of theuser to the portable telephone apparatus vary corresponding to theoperation state thereof. When the amount of fluctuation varies, it isvery difficult to optimally adjust the impedance of the antenna.

[0043] A part of the body that most approaches the antenna is an ear ofthe user. However, the size of the ears varies person by person. Thedifference of the size of the ears largely affects the performance ofthe antenna. The ears of the user cause the impedance of the antenna tolargely fluctuate. This is because the dielectric constant of ears is ashigh as 80. When an ear of the user approaches the antenna, theelectrical length of the antenna largely varies. Depending on whether ornot an ear contacts the antenna or whether the ear is close to or farapart from the antenna, the impedance largely varies. The relativeposition of an ear to the antenna largely depends on the size of theear. Thus, even if the impedance is optimized in the state that the bodyof the user approaches the antenna, the optimized antenna may be notoptimum for other people. Thus, the performance of the antenna deviatesperson by person.

[0044] Besides the above-described techniques, there are severaltechniques for optimally controlling the matching circuit correspondingto the operation state.

[0045] As the first technique, a matching circuit of the antenna isswitched to the other corresponding to the on/off state of a callbutton. This technique is based on the assumption that when the callbutton is turned on, an ear of the user is close to the antenna.

[0046] Although this technique can be accomplished with a simplestructure, it cannot deal with the variation of the size of ears of eachuser.

[0047] As the second technique, the level of a wave reflected from theantenna is detected and a matching circuit of the antenna is switched tothe other corresponding to the amount of reflection.

[0048] However, in this case, to detect the amount of reflection, it isnecessary to place a probe between the antenna and the radio circuit.This probe may cause a reflection loss, a conductor loss, and/or a lossof an RF signal to take place.

[0049] Thus, according to the above-described conventional portabletelephone apparatus, in the receiving portion, the maximum currentshould be always supplied. Thus, the current consumption is excessivelarge. When a DC offset is removed with an AC coupling capacitor, adesired signal component is also attenuated. In addition, there is atime-varying DC offset that is caused by a reflection of an externalreflector and that cannot be removed by an AC coupling capacitor. Thus,the deterioration of the reception sensitivity cannot be suppressed.

[0050] In addition, the synthesizer cannot search a blank channel with ablank channel slot in the communicating state.

[0051] In the transmitting portion, the mounting sizes of circuit partssuch as a directional coupler and a power detector other than an antennaare large. Thus, the size of the portable telephone apparatus cannot befurther decreased.

[0052] In the antenna, when the user who carries the portable telephoneapparatus approaches the antenna, the antenna characteristicdeteriorates. To solve this problem, the size of the antenna should beincreased. Alternatively, the user should be selected for the antenna.

SUMMARY OF THE INVENTION

[0053] The present invention is made from the above-described point ofview.

[0054] A first object of the present invention is to decrease the powerconsumption.

[0055] A second object of the present invention is to remove atime-varying DC offset and improve the reception sensitivity.

[0056] A third object of the present invention is to decrease themounting size of the transmitting portion.

[0057] A fourth object of the present invention is to maintain theperformance of the antenna without need to increase the size thereof andselect the user.

[0058] To accomplish the above-described objects, a first aspect of thepresent invention is a radio apparatus, comprising receiving means forreceiving a radio signal in a system band used in a radio system, asynthesizing means for sending at least all desired frequency signals inthe system band to the receiving means, a blank channel detecting meansfor detecting a blank channel of the system band, and a controllingmeans for widening a loop band width of a PLL (Phase Lock Loop) of thesynthesizing means while the blank channel detecting means is detectinga blank channel.

[0059] A second aspect of the present invention is a radio apparatus forrepeatedly transmitting and receiving a predetermined number of slotswith a plurality of radio frequency signals available in a radio systemband and data communication using a blank slot, comprising a phasesynchronizing circuit having a phase comparator for generating a voltagecorresponding to the phase difference between the phase of a referencesignal and the phase of a comparing frequency divided signal, and avoltage controlling oscillator for generating a frequency correspondingto a control voltage, a first loop filter for causing the phasesynchronizing circuit to perform a phase synchronizing operation atpredetermined speed, a second loop filter for causing the phasesynchronizing circuit to perform the phase synchronizing operation athigher speed than the predetermined speed, and a loop filter selectingmeans for connecting the first loop filter to the voltage controllingoscillator in the period of one of the slots that is used for acommunication and for connecting the second loop filter to the voltagecontrolling oscillator when the period of the slot is over.

[0060] A third aspect of the present invention is a radio apparatushaving a frequency converter, a low frequency amplifying, and ananalog/digital converter for directly converting the frequency of an RFsignal received by an antenna into a baseband signal, comprising areflection detecting means for detecting at least one of a reflectioncoefficient of the antenna and a reflection power of the power amplifierwhen an RF signal is transmitted, and a controlling means forcontrolling at least one of DC offsets of the frequency converter, thelow frequency amplifier, and the analog/digital converter correspondingto the antenna reflection coefficient or the antenna reflection powerdetected by the reflection detecting means.

[0061] A fourth aspect of the present invention is a radio apparatushaving a frequency converter, a low frequency amplifying, and ananalog/digital converter for directly converting the frequency of an RFsignal received by an antenna into a baseband signal, comprising areflection detecting means for detecting at least one of a reflectioncoefficient of the antenna and a reflection power of the power amplifierwhen an RF signal is transmitted, a storing means for storing the valueof the reflection coefficient or reflection power detected by thereflection detecting means, and a controlling means for controlling atleast one of DC offsets of the frequency converter, the low frequencyamplifier, and the analog/digital converter corresponding to the antennareflection coefficient or the antenna reflection power stored in thestoring means when the RF signal is received.

[0062] A fifth aspect of the present invention is a radio apparatus,comprising a transmitting portion having a power amplifier for sending aradio signal to an antenna, a receiving portion for receiving a radiosignal from the antenna, a transmission/reception switch for selectingone of the transmitting portion or the receiving portion, a transmissionpower detecting means, connected or capacitance coupled to a powersupply portion of the power amplifier of the transmitting portion, fordetecting a transmission power corresponding to a fluctuation of thepower supply portion, the fluctuation taking place when a radio signalis transmitted, and a controlling means for determining a transmissionpower of the transmitting portion corresponding to a transmission powerdetected by the transmission power detecting means.

[0063] A sixth aspect of the present invention is a radio apparatus,comprising a radio circuit for sending a signal to be transmitted to anantenna through a transmitting amplifier, a power supply circuit forsending a power to the radio circuit and the transmitting amplifierthrough a feeder, an ampere meter connected to the feeder, and anantenna characteristic varying means for varying a matchingcharacteristic of the antenna corresponding to a current value detectedby the ampere meter.

[0064] According to the present invention, with respect to the firstproblem of the receiving portion, a power detecting function fordetecting the power of a desired frequency band and a power detectingfunction for detecting the power of the system frequency band aredisposed. With these functions, it is determined whether or not theradio apparatus is in the worst radio wave environment. With thedetermined result, the current consumption of the receiving portion iscontrolled. The determination is made with reference to data stored in astoring device.

[0065] With respect to the second problem of the receiving portion, adigital signal processing portion has an AC capacitor so as to amplify asignal corresponding to the amount of attenuation of each frequency.

[0066] With respect to the third problem of the receiving portion, acontrol signal detecting portion has a controlling portion that detectsa reflection coefficient of the antenna or a reflection power of a poweramplifier in the transmission state and controls a DC offset of afrequency converter, a low frequency amplifier, or an analog/digitalconverter corresponding to the detected signal.

[0067] Alternatively, the controlling portion stores the reflectioncoefficient of the antenna or the reflection power signal of the poweramplifier detected in the transmission state to the storing device andcontrols the DC offset of the frequency converter, the low frequencyamplifier, or the analog/digital converter corresponding to thereflection coefficient or reflection power signal stored in the storingdevice.

[0068] Alternatively, the controlling portion subtracts a valuecorresponding to the reflection coefficient of the antenna detected bythe control signal detecting portion or a value corresponding to thereflection power of the power amplifier from a value detected by theanalog/digital converter or adds these values. Thus, according to thepresent invention, even if the situation of a reflection in the vicinityof the antenna varies, the fluctuation of the DC offset can besuppressed, thereby preventing the reception sensitivity fromdeteriorating.

[0069] With respect to the problem of the synthesizer, when thesynthesizer detects a blank channel, the loop band is widened incomparison with that in the communicating state.

[0070] With respect to the first problem of the transmitting portion, todecrease the mounting areas of a directional coupler and a powerdetector, a power coupler and a power detector that do not always havedirectional characteristics are structured in a power amplifier IC chipor a transmission/reception switch IC chip. Thus, the size of thetransmitting portion can be decreased.

[0071] As a signal for detecting a transmission power, a signalproportional to the transmission power generated in such an IC chip isused. With respect to the second problem of the transmitting portion,the amount of fluctuation of the power supply portion is detected.

[0072] With respect to the problem of the antenna, a current that flowsin a feeder line of a transmitting amplifier is measured. Correspondingto the measured current value, the matching characteristic of theantenna is varied.

[0073] These and other objects, features and advantages of the presentinvention will become more apparent in light of the following detaileddescription of a best mode embodiment thereof, as illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0074]FIG. 1 is a block diagram showing a structure for detecting thepower of a system band and the power of a desired wave and decreasingthe power consumption of a receiving portion according to the presentinvention;

[0075]FIG. 2 is a flow chart showing a controlling process of thestructure for decreasing the power consumption of the receiving portionaccording to the present invention;

[0076]FIG. 3 is a block diagram showing an example of the structure ofthe receiving portion having a self compensating function according tothe present invention;

[0077]FIG. 4 is a graph showing a frequency characteristic of an outputsignal of a frequency converter;

[0078]FIG. 5 is a graph showing a frequency characteristic having anotch due to an AC coupling operation;

[0079]FIG. 6 is a graph showing a frequency characteristic of ACcoupling capacitors;

[0080]FIG. 7 is a graph showing an invert characteristic of thefrequency characteristic shown in FIG. 6;

[0081]FIG. 8 is a graph showing a desired wave that has beenself-compensated corresponding to the present invention;

[0082]FIG. 9 is a graph showing a DC offset in the case that a localoscillation frequency de-tunes;

[0083]FIG. 10 is a block diagram showing another example of thestructure of the receiving portion having the self-compensatingfunction;

[0084]FIG. 11 is a block diagram showing the structure of a directconversion radio apparatus according to an embodiment of the presentinvention;

[0085]FIG. 12 is a schematic diagram showing a modification of the radioapparatus shown in FIG. 11;

[0086]FIG. 13 is a schematic diagram showing another modification of theradio apparatus shown in FIG. 11;

[0087]FIG. 14 is a block diagram showing the structure of a synthesizerof the radio apparatus according to an embodiment of the presentinvention;

[0088]FIG. 15 is a schematic diagram for explaining a high speed blankchannel searching operation of the synthesizer shown in FIG. 14;

[0089]FIG. 16 is a schematic diagram showing the basic concept of afront-end radio frequency IC having a sensing means;

[0090]FIG. 17 is a schematic diagram showing the basic concept of afront-end radio frequency IC having a sensing means and a powerdetector;

[0091]FIG. 18 is a schematic diagram showing the structure of a PA-ICchip according to an embodiment of the present invention;

[0092]FIG. 19 is a schematic diagram showing an example of a sensingmeans of the PA-IC chip shown in FIGS. 16 and 17;

[0093]FIG. 20 is a schematic diagram showing another example of thesensing means;

[0094]FIG. 21 is a schematic diagram showing a real example of avariable gain controlling circuit shown in FIG. 20;

[0095]FIG. 22 is a schematic diagram showing the basic structure of anSPDT switch;

[0096]FIG. 23 is a schematic diagram showing the structure of a T/Rswitch IC chip according to an embodiment of the present invention;

[0097]FIG. 24 is a schematic diagram showing an example of the sensingmeans;

[0098]FIG. 25 is a schematic diagram showing another example of thesensing means;

[0099]FIG. 26 is a schematic diagram showing the structure of the PA-ICchip according to an embodiment of the present invention;

[0100]FIG. 27 is a schematic diagram showing the structure of a T/Rswitch IC chip according to an embodiment of the present invention;

[0101]FIG. 28 is a plan view showing the structure of an IC chip thathas the power sensing device and the power detecting device shown inFIGS. 19 and 20 according to an embodiment of the present invention;

[0102]FIG. 29 is a sectional view taken along line A-A′ shown in FIG.28;

[0103]FIG. 30 is a schematic diagram showing the structure of which aline width of a metal layer is narrower than a power line so as toadjust a coupling capacitance;

[0104]FIG. 31 is a schematic diagram showing the structure of which aline width of a metal layer is wider than a power line so as to adjust acoupling capacitance;

[0105]FIG. 32 is a schematic diagram showing the structure of which aline length of a metal layer is varied so as to adjust a couplingcapacitance;

[0106]FIG. 33 is a schematic diagram showing the structure of which aforming direction of a metal layer is varied so as to adjust a couplingcapacitance;

[0107]FIG. 34 is a block diagram showing the structure of a portableradio apparatus according to another embodiment of the presentinvention;

[0108]FIG. 35 is an external view showing a radio apparatus model usedin an experiment;

[0109]FIG. 36 is a graph showing the relation between a currentconsumption and operation states of the portable radio apparatus shownin FIG. 35;

[0110]FIG. 37 is a graph showing the relation between a reflectioncoefficient at an input edge of the antenna viewed from the feeder lineside and operation states of the portable radio apparatus;

[0111]FIG. 38 is a graph showing the relation between an averageradiation gain on a horizontal plane of the portable radio apparatus andoperation states thereof; and

[0112]FIG. 39 is a schematic diagram showing the structure of an antennamatching circuit.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0113] Next, with reference to the accompanying drawings, an embodimentof the present invention will be described.

[0114]FIG. 1 is a block diagram showing the structure of a receivingportion of a direct modulation type portable radio apparatus(hereinafter simply referred to as radio apparatus) according to anembodiment of the present invention. In the following description, thedirect demodulation type radio apparatus will be described. However, thepresent invention can be applied to a heterodyne type radio apparatusand so forth.

[0115] As shown in FIG. 1, the radio apparatus comprises a low noiseamplifier (hereinafter referred to as LNA), a band pass filter(hereinafter referred to as BPF), a mixer (as a frequency convertingmeans) (hereinafter referred to as MIX), buffer amplifiers (hereinafterreferred to as BUFF1 and BUFF2), low pass filters (hereinafter referredto as LPF1 and LPF2), power detectors (hereinafter referred to as RSSI1and RSSI2 (RSSI: Received Signal Strength Indicator)), a subtractingdevice 10, a determining device 11, a delaying device 12, and a currentcontrolling means 13.

[0116] The LPF1 passes a predetermined signal band of the system band.In the case of the PHS (Personal Handyphone System) used in Japan, thepredetermined band is around 100 kHz band. The RSSI1 detects the powerof the signal band. The LPF2 passes all the system band. The LPF2 shouldbe a filter that passes all frequencies of at least the system band. TheRSSI2 detects the power of the system band. The delaying device 12delays an input signal so as to control the signal from the next frameor slot. Instead of the LPF1 and LPF2, band pass filters (hereinafterreferred to as BPF1 and BPF2) may be used. In addition, instead of thesubtracting device 10, a dividing device may be used.

[0117] To decrease the amount of a current that flows in the circuitblock of the receiving portion, it is necessary to determine that theradio apparatus is not in the worst radio wave environment. To do that,the RSSI1 and RSSI2 are provided. The RSSI1 detects the power of thedesired band. In contrast, the RSSI2 detects the power of the systemband. The determining device 11 obtains the difference of the powerdetected by the RSSI1 and the power detected by the RSSI2 or the ratiothereof so as to determine whether or not the radio apparatus is in theworst radio wave environment. There is no assurance of the normaloperation of the circuit in the case that the amount of current ishalved in the non-worst radio wave environment. Thus, the difference ofthe power detected by the RSSI1 and the power detected by the RSSI2 orthe ratio thereof are divided into several levels and supplied to theLNA and the MIX. The distortion characteristic of the circuit blockcorresponding to the designated current corresponding to the differenceor ratio of the RSSI1 and RSSI2 is written to a table stored in a memory(not shown) of the determining device 11 beforehand. With reference tothe designated current value on the table, a relevant current issupplied to the LNA and the MIX. When the number of levels of thecurrent to be designated is small, it is not always necessary toreference the table.

[0118] Next, with reference to the flow chart shown in FIG. 2, theoperation of the receiving portion will be described.

[0119] It is assumed that each frame has one reception slot. With onlythe reception slot, the current is controlled. In addition, forsimplicity, the levels of the current to be designated are only twomodes that are a normal current (for the worst radio wave environment)mode and a low current mode.

[0120] As shown in FIG. 2, in the receiving portion, the RSSI1 detectsthe power in the desired band at a slot end (at step S201). On the otherhand, the RSSI2 detects the power in the system band. The RSSI1 and theRSSI2 send the detected powers to the subtracting device 10.

[0121] The subtracting device 10 subtracts the power detected by theRSSI1 from the power detected by the RSSI2 and sends the subtractedresult to the determining device 11. When the dividing device is usedinstead of the subtracting device 10, the dividing device divides thepower detected by the RSSI2 by the power detected by the RSSI1 and sendsthe divided result to the determining device 11.

[0122] The determining device 11 determines whether or not thesubtracted result or the divided result is equal to or larger than apredetermined value A (at step S202).

[0123] When the subtracted result is equal to or larger than thepredetermined value A (namely, the determined result at step S202 isYes), the determining device 11 determines that the radio waveenvironment is bad and designates the normal current mode (in which thenormal current is supplied) (at step S203). The determining device 11applies the determined result to the next reception slot (at step S204).

[0124] When the subtracted value or the divided value detected at thenext reception slot is smaller than the designated value A (namely, thedetermined result at step S202 is No), the determining device 11designates the low current mode (at step S205) so as to decrease theamount of currents that flow in the LNA and the MIX (at step S206).

[0125] To decrease the amount of current, the resistance or definedvoltage of a bias circuit (not shown) that designates a bias current ofthe LNA and the MIX is varied. In the following description, the amountof current is decreased in the above-described manner.

[0126] In this embodiment, the amount of current is detected each frameprior. Alternatively, the amount of current may be detected one slotprior. In this case, the difference of the output level of the desiredwave detected one frame prior and the output level of the system band ofthe current frame or the ratio thereof is obtained.

[0127] To accomplish the present invention, it is preferable todesignate the normal current level as the initial current level.However, when a blank channel is detected, if all channels are blank, itcan be estimated that there is no unnecessary wave in the system. Thus,in this case, the low current level can be designated as the initiallevel.

[0128] On the other hand, since the LPF2 passes all the system band, theratio of the system band to the desired wave is large. Thus, white noise(or thermal noise) increases in the LPF2.

[0129] When the white noise increases, the determining device 11 maymistaken the number of radio waves in the system. To solve this problem,the power component of the white noise with a widened band is subtractedfrom the value detected by the RSSI2 so as to compensate the value ofthe power detected by the RSSI2. As a compensating technique, the powercomponent is simply subtracted from the value of the power detected bythe RSSI2. Alternatively, the value of the power detected by the RSSI2may be compensated using a table containing the power component of thewhite noise.

[0130]FIG. 3 is a block diagram showing the receiving portion of theradio apparatus according to another embodiment of the presentinvention.

[0131] Referring to FIG. 3, the radio apparatus comprises an antenna101, a radio frequency amplifier 102, a radio frequency filter 103, afrequency converter 104, frequency converters 105 and 106, a localoscillator 107, a π/2 phase shifter 108, low frequency filters 109 and110, low frequency amplifiers 111 and 112, A/D converters 113 and 114,multiplying devices 115 and 116, a memory 118 (as a storing means),capacitors 119 to 124, and a local oscillator 125. The memory 118 storesan inverse characteristic of an overall AC-coupled frequencycharacteristic of the baseband portion from the frequency converter 105to the A/D converter 113 and an inverse characteristic of an overallAC-coupled frequency characteristic of the baseband portion from thefrequency converter 106 to the A/D converter 114.

[0132] The radio frequency amplifier 102 improves the noise figure ofthe radio portion. A circuit block composed of the frequency converters105 and 106, the local oscillator 107, the π/2 phase shifter 108, and soforth is referred to as an orthogonal demodulating portion. Thecapacitors 119 to 124 connected to a downstream stage of the frequencyconverters 105 and 106 are disposed so as to remove a DC component.

[0133] In this receiving portion, a radio frequency signal received fromthe antenna 101 is sent to the radio frequency amplifier 102. The radiofrequency amplifier 102 amplifies the radio frequency signal with apredetermined gain. The amplified signal is sent to the frequencyconverter 104 through the radio frequency filter 103 that is an imagesuppressing filter.

[0134] On the other hand, the local oscillator 125 generates a referencecarrier signal and sends the reference carrier signal to the frequencyconverter 104. The frequency converter 104 multiplies the receivedsignal by the reference carrier signal and thereby converts the receivedsignal into an intermediate frequency signal. The intermediate frequencysignal is converted into a baseband signal by the orthogonaldemodulating portion composed of the frequency converters 105 and 106,the local oscillator 107, and the π/2 phase shifter 108. In other words,the two frequency converters 105 and 106 generate two baseband signalsof I and Q channels that have the same frequency as the intermediatefrequency signal sent from the local oscillator 107 and that have aphase difference of π/2.

[0135] The baseband signal of I channel obtained from the frequencyconverter 105 is sent to the low frequency filter 109 through thecapacitor 119. The low frequency filter 109 performs the anti-aliasingprocess for the baseband signal of I channel. The resultant signal issent to the low frequency amplifier 111 through the capacitor 121. Thelow frequency amplifier 111 amplifies the received signal with apredetermined gain. The amplified signal is sent to the A/D converter113 through the capacitor 123. The A/D converter 113 converts thereceived signal as an analog signal into a digital signal. The resultantdigital signal is sent to the multiplying device 115.

[0136] On the other hand, as with the baseband signal of I channel, thebaseband signal of Q channel obtained from the frequency converter 106is sent to the multiplying device 116 through the capacitor 120, the lowfrequency filter 110, the capacitor 122, the low frequency amplifier112, the capacitor 124, and the A/D converter 114. The low frequencyfilters 109 and 110 may select a channel.

[0137] An inverse characteristic of the overall AC-coupled frequencycharacteristic of the baseband portion from the frequency converter 105to the A/D converter 113 is sent from the memory 118 to the multiplier115 of I channel in synchronization with the digital signal. Themultiplier 115 multiplies the signal received from the A/D converter 113by the inverse characteristic received from the memory 118.

[0138] An inverse characteristic of the overall AC-coupled frequencycharacteristic of the baseband portion from the frequency converter 106to the A/D converter 114 is sent from the memory 118 to the multiplier116 of Q channel in synchronization with the digital signal. Themultiplier 116 multiplies the signal received from the A/D converter 114by the inverse characteristic received from the memory 118.

[0139] The detector 117 demodulates the multiplied signals received fromthe multiplier 115 of I channel and the multiplier 116 of Q channel intooriginal data.

[0140] Next, individual signals with respect to the above describedoperation will be described.

[0141] As shown in FIG. 4, a desired baseband signal (hereinafterreferred to as desired wave) obtained from the frequency converters 105and 106 overlaps with a DC component 305. In FIG. 4, a hatched regionrepresents the level of thermal noise 304.

[0142] The capacitors 119 to 124 disposed in the downstream stage of thefrequency converters 105 and 106 remove the DC component 305 from thedesired wave 301. The capacitances of the capacitors 119 to 124 aredesignated so that a frequency characteristic 302 of the desired wave301 is obtained.

[0143] When the DC component 305 is removed by the AC couplingcapacitors 119 to 124, a signal component 303 as a part of the desiredsignal 301 is lost along with the DC component 305. Thus, before thedesired wave 301 (namely, output signals of the A/D converters 113 and114) is sent to the multipliers 115 and 116, as shown in FIG. 5, a notch306 takes place in the desired wave 301. Likewise, a notch 307 takesplace in thermal noise 304.

[0144] Although the output signals of the A/D converters 113 and 114have the notch 306, since a signal component affected by the notch 306is known, when the memory 118 stores an inverse characteristic necessaryfor interpolating the affected portion and the multiplying devices 115and 116 multiply the desired wave 301 by the inverse characteristicstored in the memory 118, the original signal can be almost exactlyreproduced.

[0145] Next, the inverse characteristic stored in the memory 118 will bedescribed.

[0146] In FIG. 6, a reference numeral 801 represents a frequencycharacteristic of which baseband signals obtained from the frequencyconverters 105 and 106 are AC-coupled by the capacitors 119 to 124 untilthe signals are sent to the A/D converters 113 and 114.

[0147] When the frequency characteristic 801 is AC-coupled, a DCcomponent whose value is 0 takes place. An inverse characteristic of thefrequency characteristic 801 is represented by reference numeral 802 asshown in FIG. 7. Since the value of the inverse characteristic 802 as aDC component is infinite, the characteristic 802 cannot be stored asdata to the memory 118.

[0148] In the characteristic 802, a portion of the DC component thatexceeds a predetermined level is removed and used as an inversecharacteristic corresponding to the required compensation accuracy.

[0149] In an example shown in FIG. 7, a DC component 803 is removed fromthe inverse characteristic 802 of the frequency characteristic that hasbeen AC-coupled. The resultant portion is treated as an inversecharacteristic 804. Thus, in the desired wave 301 of which the inversecharacteristic 804 has been multiplied by the output signals of the A/Dconverters 113 and 114, a compensation error corresponding to thelimited portion of the DC component of the inverse characteristic takesplace. In other words, the compensation error corresponding to thelimited portion of the DC component of the inverse characteristic 804causes notches 701 and 702 to take place in the desired wave 301 and thethermal noise 304, respectively.

[0150] However, it is clear that the unnecessary DC component has beencompletely removed and that the notch 701 of the signal component ismore alleviated than the notch 306 shown in FIG. 5. Since the DC offsetof I channel is different from the DC offset of Q channel, the selfcompensating operation should be performed for each of I and Q channels.An advantage of the self compensating function of the DC component is inthat its effect is not lost even if the reference carrier frequencyobtained from the local oscillator 107 shown in FIG. 3 is offset from adesired value.

[0151] When the frequency obtained from the local oscillator 107 isoffset from the desired value, the center frequency of the basebandsignal (desired wave) obtained from the frequency converters 105 and 106is offset from the DC component as shown in FIG. 9.

[0152] As shown in FIG. 9, the center frequency of a desired wave 601 isoffset from the DC component 306 by a distance 602. The distance 602 isequal to the frequency offset against the desired frequency of the localoscillator 107. However, as is clear from FIG. 9, even if the centerfrequency of a signal converted to a baseband signal is offset from theDC component, theoretically the DC component is not offset. Thus,corresponding to the frequency characteristic 302 of the AC couplingcapacitors 119 to 124, the DC component 305 is completely removed.Thereafter, the output signals of the A/D converters 113 and 114 aremultiplied by the inverse characteristic 804 stored in the memory 118.Thus, as with the case that the local oscillator 107 does not have afrequency offset, the DC component 305 can be removed from the desiredwave 301 without a large notch. The inverse characteristic 804 that havebeen measured can be stored in the memory 118.

[0153] Next, with reference to FIG. 10, the receiving portion of theradio apparatus according to another embodiment of the present inventionwill be described. The receiving portion of this embodiment furthercomprises a sweep oscillator 910, a switch 902, and a calculating device907. The sweep oscillator 901 is connected to the circuits of I channeland Q channel through the switch 902. The sweep oscillator 901 sweepsfrequencies in the range that the frequency characteristic 801 of ACcoupled signals that are output from the frequency converters 105 and106 and the A/D converters 113 and 114 becomes flat. With the sweepingoperation, the frequency characteristic 801 of the AC coupled signals ofI channel and Q channel can be obtained. The obtained frequencycharacteristic 801 is sent to the calculating device 907 branched fromthe A/D converters 113 and 114. The calculating device 907 calculatesthe inverse characteristic 804 shown in FIG. 7 with the frequencycharacteristic 801 of the measured AC coupled signal. The calculatedinverse characteristic 804 are stored in the memory 118. The frequencycharacteristic can be measured by the sweep oscillator 901 while asignal is not being received.

[0154] According to this embodiment, even if the frequencycharacteristic 801 of the AC coupled signal vary due to a temperaturecharacteristic, the inverse characteristic 804 can be more flexiblyobtained and the DC offset can be compensated.

[0155] In this embodiment, the heterodyne type receiving portion wasdescribed. However, a direct modulation type receiving portion can beused. In this case, a transient response of a time-varying DC offset dueto a reflector cannot be handled. However, with the above-describedcountermeasures, a sufficient characteristic may be obtained in aparticular radio system.

[0156] Next, a method for removing a time-varying DC offset caused by areflector will be described (the time-varying DC offset is a problem tobe solved in the direct conversion type radio apparatus).

[0157]FIG. 11 is a block diagram showing the structure of a directconversion type radio apparatus (hereinafter referred to as radioapparatus) according to an embodiment of the present invention.

[0158] Referring to FIG. 11, the radio apparatus comprises an antenna101, a transmission/reception switch 170, a receiving portion 129, atransmitting portion 137, and a DC offset controlling circuit 139. Thereceiving portion comprises a radio frequency amplifier 102, frequencyconverters 105 and 106, a local oscillator 130, a π/2 phase shifter 131,a baseband filter 109, low frequency amplifiers 111 and 112, andbaseband signal processing circuits 135 and 136. The local oscillator130 generates a local signal. Each of the frequency converters 105 and106 has a DC offset control terminal 132-1. Each of the low frequencyamplifiers 111 and 112 has a DC offset control terminal 132-2. Each ofthe baseband signal processing circuits 135 and 136 has a DC offsetcontrol terminal 132-3. The baseband signal processing circuits 135 and136 have analog/digital converters 113 and 114 and adding/subtractingcircuits 133 and 134, respectively.

[0159] The transmitting portion 137 comprises a band pass filter 150, adirectional coupler 172, a power amplifier 151, a variable attenuator152, a power detector 173, a power controlling circuit 171, an addingdevice 156, frequency converters 157 and 158, low pass filters 159 and160, digital/analog converters 161 and 162, and a transmission signalgenerator 138. The DC offset controlling circuit 139 is connected to thedirectional coupler 172 and the control terminals 132-1, 132-2, and132-3.

[0160] Next, the basic operation of the transmitting portion of theradio apparatus according to this embodiment will be described.

[0161] In the radio apparatus, when a signal is transmitted, thetransmission/reception switch 170 is placed on the transmitting portionside. A transmission wave received from the transmission signalgenerator 138 is amplified by the power amplifier 151. The resultantsignal is transmitted from the antenna 101 through the directionalcoupler 172 and the transmission/reception switch 170.

[0162] In this embodiment, the TDD system of which the frequency of thetransmission signal is the same as the frequency of the reception signalwill be described. When a signal is transmitted, the directional coupler172 measures the power reflected from the antenna 101. In addition, thedirectional coupler 172 measures the power propagated to the antenna101. The measured results are sent to the DC offset controlling circuit139. The DC offset controlling circuit 139 obtains a reflectioncoefficient of the antenna 101 with the reflection power and thepropagation power. In the TDD system, the frequency of the transmissionsignal is the same as the frequency of the reception signal. Thus, whena signal is transmitted, if the reflection power is large, thereflection power of a local signal in the receiving mode of the antenna101 is large. In contrast, when the reflection power is small, thereflection power of the local signal in the receiving mode of theantenna 101 is small. Thus, when a signal is transmitted, the reflectionpower in the transmitting mode of the antenna 101 can be obtained. Thus,the amount of the reflection of the local signal to the receivingportion can be obtained.

[0163] When the reflection wave is large, the DC offset controllingcircuit 139 sends a control signal that causes the DC offset to decreaseand that is proportional to the reflected power to the DC offset controlterminals 132-1 of the frequency converters 105 and 106, therebydecreasing the DC offset in the receiving portion.

[0164] In the radio apparatus according to the embodiment, when a signalis transmitted in the TDD system, the directional coupler 172 measuresthe propagation power to the antenna 101 and the reflection power fromthe antenna 101, obtains the reflection coefficient of the antenna 101with the propagation power and the reflection power, and sends thereflection coefficient to the receiving portion. Thus, when a signal isreceived just after a signal is transmitted, the receiving operation isperformed in the state that the DC offset is decreased due to anexternal reflector. Thus, the reception sensitivity at which thereceiving operation is improved in comparison with the case that such aprocess is not performed. In addition, since a signal can be received inthe state that an DC offset is decreased, it is not necessary todisposed many AC coupling capacitors in the circuit.

[0165] In the above example, the controlling operations of the frequencyconverters 105 and 106 were described. Alternatively, when a controlsignal is sent to one of the DC offset control terminals 132-2 and 132-3of the low frequency amplifiers 111 and 112 and the analog/digitalconverters 113 and 114, the same effect as the case that the frequencyconverters 105 and 106 are controlled can be obtained. In other words,if necessary, a DC offset can be compensated in upstream stages of thefrequency converters 105 and 106.

[0166] Next, with reference to FIG. 12, a radio apparatus according to amodification of the embodiment shown in FIG. 11 will be described.

[0167] As shown in FIG. 12, in this modification, a memory 141 isdisposed between a DC offset controlling circuit 139 and a directionalcoupler 172. The memory 141 stores data for causing a control voltagecorresponding to the reflection power or reflection coefficient of theantenna 101 to be generated. Thus, when the memory 141 stores controldata for decreasing the DC offset corresponding to the reflection powerof the antenna 101, the control data is sent to the DC offsetcontrolling circuit 139. Thus, the DC offset controlling circuit 139 candecrease the DC offset in a shorter time period than that of theembodiment shown in FIG. 8 without need to calculate the reflectioncoefficient.

[0168] Next, with reference to FIG. 13, a radio apparatus according toanother modification of the embodiment shown in FIG. 11 will bedescribed.

[0169] In this modification, a baseband signal processing circuit 135performs a DC offset decreasing process instead of the DC offsetcontrolling circuit 139. In FIG. 13, for simplicity, a baseband signalprocessing circuit 136 is omitted.

[0170] In this modification, adding/subtracting circuits 133 and 134 add(or subtract) the value corresponding to the propagation power of thepower amplifier 151 and the value corresponding to the reflection powerof the antenna 101 and the values received from the analog/digitalconverters 113 and 114 so as to decrease the DC offset. In other words,when the output values of the analog/digital converters 113 and 114 areadded or subtracted, a DC value is analogously offset.

[0171] According to this modification, the same effect as the embodimentshown in FIG. 11 can be obtained without need to connect a special DCoffset controlling circuit 139 to an analog circuit such as a frequencyconverter and a low frequency converter. In the above-describedembodiment, TDD system was described. In the case that the frequencyband of a transmission signal is the same as the frequency band of areception signal, when the amount of reflection in the transmittingstate is measured, the same effect can be obtained.

[0172] Next, the synthesizer of the radio apparatus of the radioapparatus will be described.

[0173]FIG. 14 is a block diagram showing the structure of a synthesizerof the radio apparatus according to a first embodiment of the presentinvention.

[0174] Referring to FIG. 14, the synthesizer comprises a referenceoscillator 1101, a reference frequency divider 1103, a phase comparator1105, a normal mode loop filter 1151, a high speed mode loop filter1152, a switch 1153, a VCO 1109, and a comparing frequency divider 1111.Since the basic loop operation of the synthesizer is the same as that ofa conventional synthesizer, its description is omitted.

[0175] In the synthesizer according to the embodiment, when the switch1153 is placed on the normal mode loop filter side, a normal loop modetakes place. In this case, the VCO 1109 outputs a signal with a lowphase-to-noise characteristic. However, in this mode, the frequencyswitching operation takes a time.

[0176] On the other hand, when the switch 1153 is placed on the highspeed mode loop filter side, a high speed loop mode (blank channelsearch mode) takes place. In this mode, although the phase-to-noisecharacteristic of an output signal of the VCO 1109 deteriorates, thefrequency switching operation is quickly performed.

[0177] Next, the operation of the synthesizer of the radio apparatusaccording to the embodiment will be described. FIG. 15 is a schematicdiagram showing the structure of slots in the TDMA system.

[0178] As shown in FIG. 15, one frame 1160 is composed of four receptionslots R1 to R4 and four transmission slots T1 to T4. One slot is denotedby reference numeral 1161. It is assumed that a communication is madewith one reception slot R1 and one transmission slot T1. In addition, itis assumed that a frequency of a communication channel is denoted by f1.

[0179] The synthesizer searches a blank channel in the following manner.

[0180] In the period of the reception slot R1, the synthesizer operatesin the normal mode with a high phase-to-noise characteristic. After theperiod of the reception slot R1, the switch 1153 switches the normalmode to the high speed mode.

[0181] When a frequency f2 that is different from the frequency of thecommunication channel is designated to the synthesizer, it searches ablank channel. Since the high speed mode has been selected, thesynthesizer switches the current frequency to the desired frequency athigh speed and searches a blank channel.

[0182] After the synthesizer has searched a black channel at frequencyf2, it switches the frequency f2 to another frequency f3 and searches ablank channel. The synthesizer repeats such an operation and searchesblank channels at a plurality of frequencies. Before the transmissionslot T1 takes place, the synthesizer restores the original communicationchannel f1. At the same time, the synthesizer switches the high speedmode to the normal mode. In the period of the transmission slot T1, thesynthesizer operates in the normal mode with the high phase-to-noisecharacteristic. The synthesizer repeats the above-described operationand searches blank channels during the communication. While thesynthesizer is searching a blank channel, since it operates in the highspeed mode, the S/N (signal-to-noise ratio) of the synthesizer is nothigh and thereby the reception sensitivity thereof deteriorates.However, since the phase-to-noise characteristic necessary fordetermining whether there is a blank channel is alleviated in comparisonwith that in the communicating state, the synthesizer can search a blankchannel in the high speed mode. In the above-description, the loopcharacteristic was switched by switching the frequency characteristic ofthe loop filter. Alternatively, by switching the sensitivity of thephase comparator, the loop characteristic may be switched. In addition,a blank channel may be searched in for example one slot.

[0183] When the synthesizer searches a blank channel in the high speedmode, if all channels are blank, it can be determined that there is nointerference wave in the vicinity of the system band. Thus, as anoperation for detecting the radio wave environment, the black channelsearching operation can be used. In other words, when all channels areblack, the current consumption of the receiving portion can bedecreased.

[0184] In this case, the searched result of a blank channel is sent tothe determining device 11 shown in FIG. 1. The determining device 11determines the current mode and controls the amount of current that flowin the LNA and the MIX.

[0185] Next, with reference to FIGS. 16 to 26, the transmitting portionwill be described.

[0186]FIG. 16 is a schematic diagram showing the basic concept of an ICchip that has a power amplifier or a transmission/reception switch.

[0187] In FIG. 16, reference numeral 1200 is an IC chip. When the ICchip 1200 is for example a power amplifier IC chip (hereinafter referredto as PA-IC chip), RF signals received from the frequency converters 157and 158 show in FIG. 11 are sent to an input terminal IN of the IC chip1200. An RF signal amplified by the PA-IC chip 1200 is sent to an outputterminal OUT. The IC chip 1200 has a sensing means 1201 that senses anoutput power. A signal proportional to the power sensed by the sensingmeans 1201 is sent to a power detector DET as a signal processing meansfrom a terminal other than the output terminal OUT.

[0188] In FIG. 16, when the IC chip 1200 is a transmission/receptionswitch (hereinafter referred to as T/R switch), an RF signal receivedfrom the power amplifier PA is sent to an input terminal IN of the ICchip 1200. An RF signal received from a sensing means 1201 through aninput terminal IN is sent to an output terminal OUT. As with the PA-ICchip, the sensing means 1201 senses a signal proportional to the powerof the RF signal. The sensed signal is sent to a signal processing means(for example, an output power detector DET) from a terminal other thanthe output terminal OUT.

[0189] Next, with reference to FIG. 17, an IC chip according to amodification of the structure shown in FIG. 16 will be described.

[0190] In the example shown in FIG. 16, the output power detector DET isdisposed outside the IC chip 1200. However, in this modification, apower detecting function of an output power detector DET as a signalprocessing means 1202 is structured as an IC chip along with a sensingmeans 1201. The structure of the sensing means 1201 shown in FIG. 17 isthe same as the structure of the sensing means 1201 shown in FIG. 16.

[0191] In this modification, a signal sensed by the sensing means 1201is sent to the output power detecting means 1201 structured in the sameIC chip.

[0192] The output power detecting means 1202 converts the frequency ofan output power to a low frequency corresponding to a sense signal andsends a signal corresponding to the output power to a power controllingcircuit (CONT) 171. Since the output power detecting means 1202 performsa signal process such as a frequency converting process, the outputpower detecting means 1202 is referred to as signal processing means. InFIGS. 16 and 17, the PA-IC chip or the T/R switch IC chip are not alwaysdifferent IC chips. Instead, either the PA-IC chip or the T/R switch ICchip may be structured as an IC chip.

[0193]FIG. 18 is a schematic diagram showing the basic concept of thestructure of the PA-IC chip shown in FIG. 16.

[0194] In FIG. 18, RF signals received from frequency converters 157 and158 are sent to a power amplifier PA 151 through an input terminal IN.An output signal of the power amplifier PA 151 is sent to a band passfilter BPF through an output terminal OUT.

[0195] A power supply terminal VDD1 in an IC chip 1200 is a terminal forsupplying a power to the power amplifier PA 151. A ground terminal GND1is a ground terminal of the power amplifier PA 151. An external groundterminal GND and an external power supply terminal VDD are separatedfrom a terminal GND and a terminal VDD1 so as to represent a strayinductance, resistance, and capacitance that take place among circuitsstructured as an IC chip. In other words, a stray impedance Zvdd 1203takes place between the terminal VDD and the terminal VDD1. In addition,a stray impedance Zgnd 1204 takes place between the terminal GND and theterminal GND1.

[0196] In FIG. 18, a terminal s1 is a terminal for obtaining a signalproportional to the power of an RF signal of the power amplifier PA 151.The terminal s1 is connected to the power supply terminal VDD1 through asensing means 1201 shown in FIG. 16. In this example, a signalproportional to the product of the stray impedance Zvdd 1203 and aninstantaneous current of the power amplifier PA is measured at the powersupply terminal VDD1. Since a varied portion of the instantaneouscurrent of the power amplifier PA 151 is proportional to an output powerof the power amplifier PA 151, an AC component measured at the terminalVDD1 is proportional to the output power of the power amplifier PA 151.

[0197] Next, the structure of the sensing means 1201 will be described.With an AC component measured at the terminal VDD1, a signalproportional to the output power of the power amplifier PA 151 isobtained. Thus, as the simplest structure, as shown in FIG. 19, acapacitor C1 may be disposed between the terminal VDD1 and the terminals1.

[0198] In this case, the terminal s1 is connected to a power detectingcircuit DET described in the related art reference. The capacitor thatdoes not have a directional characteristic can be used for detecting apower since a coupler that does not have a directional characteristic isnot always required.

[0199] In the structure shown in FIG. 19, the sensing means 1201 can bestructured with only the capacitor C1. Thus, a signal proportional tothe output power can be obtained. The sensing means 1201 may be a diode,a resister, or the like.

[0200] Since the stray impedance Zvdd1 203 and the stray impedance Zgnd1204 vary depending on the mounting method of the PA-IC chip, theproportional coefficient depends on the mounting method thereof. Thus,the value of the power detected from the power detector DET may varydepending on the mounting method of the PA-IC chip. The level of thesignal detected from the terminal VDD1 is around −50 dB of the outputpower of the RF signal. Thus, since the signal level is relatively low,the power controlling circuit (CONT) 171 cannot receive a low frequencydetection signal from the power detector DET.

[0201] To solve this problem, as shown in FIG. 20, a sensing means 1201may be structured with a variable gain radio frequency amplifier (AMP)1205 that is tandem-connected to the capacitor C1 and then connected toa terminal s1.

[0202] To match the output signal of the power detecting circuit DETwith the dynamic range of the power controlling circuit (CONT) 171, thevariable gain radio frequency amplifier (AMP) 1205 is connected to thenext stage of the capacitor C1. The variable gain radio frequencyamplifier (AMP) 1205 has a gain adjustment terminal 1206. When a controlsignal is sent from the power controlling circuit (CONT) 171 to the gainadjustment terminal 1206, an output signal corresponding to the controlsignal can be obtained. Thus, when the IC chip is mounted, the amplitudeof the power detection signal can be suppressed from fluctuating.Consequently, a power detection signal whose signal level is high andstable is sent to the power controlling circuit (CONT) 171. Thus, thepower controlling circuit (CONT) 171 sufficiently detects the powerdetection signal.

[0203] In the circuit structure shown in FIG. 20, since the variablegain radio frequency amplifier (AMP) 1205 is tandem-connected to thecapacitor C1, the power controlling circuit (CONT) 171 can sufficientlydetect the power detection signal. Thus, the circuit can be practicallystructured as an IC chip.

[0204] Although the variable gain radio frequency amplifier (AMP) 1205formed as an IC chip also consumes a power, it is sufficiently smallerthan the power consumption of the power amplifier (PA) 151. Thus, thepower consumption of the variable gain radio frequency amplifier (AMP)1205 can be omitted in the transmitting portion.

[0205] Next, with reference to FIG. 21, the real structure of thevariable gain radio frequency amplifier (AMP) 1205 will be described.

[0206] Referring to FIG. 21, VDD2 is a voltage source. A positiveelectrode of a voltage source VDD2 is connected to a base terminal of atransistor Q1. A negative electrode of the voltage source VDD2 isconnected to a ground terminal GND of the IC chip. An emitter terminalof the transistor Q1 is connected to an input terminal in. In addition,the emitter terminal of the transistor Q1 is connected to a groundterminal GND1 through a variable current source I1. A gain controlsignal is sent from the gain adjustment terminal 1206 to the variablecurrent source I1. A collector terminal of the transistor Q1 isconnected to a power supply terminal VDD1 of the IC chip through a loadimpedance Z1. In addition, the collector terminal of the transistor Q1is connected to a base terminal of a transistor Q2 as a buffer. Acollector terminal of the transistor Q2 is connected to the power supplyterminal VDD1. An emitter terminal of the transistor Q2 is connected tothe ground terminal GND1 through a constant current source I2. Inaddition, the emitter terminal of the transistor Q2 is connected to anoutput terminal an output terminal out through a capacitor C3 of the DCblock. In this circuit structure, the gain G can be approximatelyobtained by the following expression.

G=gm(Q1)×Z1=i1,dc×Z1/Vt  (1)

[0207] where i1,dc represents a current that flows in the variablecurrent source I1; and Vt represents a thermal voltage.

[0208] Thus, when the current i1,dc of the variable current source I1 isvaried corresponding to a gain control signal received from the gainadjustment terminal 1206, the gain of the signal received from thevariable gain radio frequency amplifier (AMP) 1205 can be adjusted.

[0209] Next, based on the basic concept shown in FIG. 16, severalexamples of which the T/R switch and the sensing means are structured asan IC chip will be described.

[0210] As one of the most common circuits of which the T/R switch isstructured as an IC chip, a single-pole-dual-throw (SPDT) switch isknown. FIG. 22 shows a basic circuit of the SPDT switch IC chip.

[0211] As shown in FIG. 22, the SPDT switch IC includes a plurality ofswitch devices Q10 to Q13. The switch devices Q10 to Q13 are connectedto various connection terminals disposed on an outer surface of the ICchip. The various connection terminals are for example a transmittingportion input terminal Tin, a receiving portion output terminal Rin, anantenna terminal ANT, a ground terminal GND1, an input terminal cont1,and an input terminal cont2. The antenna terminal ANT functions as anoutput terminal of the transmitting portion and an input terminal of thereceiving portion. The antenna terminal ANT is connected to the antenna101. The ground terminal GND1 is a ground terminal of the IC chip.Control signals that have a complementary relation are input to theinput terminals cont1 and cont2. The control signals cause the receivingmode and the transmitting mode to be switched. When the signal level atthe input terminal cont1 is high “H” and the signal level at the inputterminal cont2 is low “L”, the switch devices Q11 and Q12 are connectedand the switch devices Q10 and Q11 are disconnected. A signal receivedfrom the antenna terminal ANT is sent to the output terminal Rin of thereceiving portion.

[0212] On the other hand, when the signal level at the input terminalcont1 is low “L” and the signal level at the input terminal cont2 ishigh “H”, the switch devices Q11 and Q12 are disconnected and the switchdevices Q10 and Q13 are connected, a signal received from the inputtingterminal Tin of the transmitting portion is sent to the antenna terminalANT.

[0213]FIG. 23 shows a T/R switch IC chip of which a sensing circuit as asensing means for sensing a signal proportional to the power of atransmission signal is disposed in the SPDT switch IC chip.

[0214] Referring to FIG. 23, in the T/R switch IC chip 1200, a sensingmeans 1201 is connected between a source terminal of a switch device Q12and a ground terminal GND1. The T/R switch IC device 1200 has a terminalout for outputting a detected result of the sensing means 1201.

[0215]FIGS. 24 and 25 show real structures of the sensing means 1201.

[0216] Referring to FIG. 24, as an example of the sensing means 1201, animpedance circuit Z is disposed between a source terminal of a switchdevice Q12 and a ground terminal GND1. The impedance circuit Z iscomposed of a resister, a capacitor, and/or an inductance that areconnected in series or in parallel. In this example, a terminal out isconnected between the impedance circuit Z and a source terminal of theswitch device Q12.

[0217] Next, the operation of the IC chip 1200 will be described.

[0218] When a signal is transmitted, the signal level at the inputterminal cont1 is low “L” and the signal level at the input terminalcont2 is high “H”, the switch device Q12 is disconnected. However, sincean RF signal is input to the input terminal Tin of the transmittingportion, the capacitor between the source terminal and the drainterminal of the switch device Q12 or the capacitor between the sourceterminal and the gate terminal and the capacitor between the gateterminal and the drain terminal are connected in series, the RF signalleaks out from the terminal out. Since the leakage current flows in theimpedance Z, a voltage proportional to the leakage current takes place.Since the leakage current is proportional to the power of the RF signal,a signal proportional to the power of the RF signal can be obtained fromthe terminal out.

[0219]FIG. 25 shows another example of the sensing means 1201. Referringto FIG. 25, a variable gain radio frequency amplifier (AMP) is connectedbetween an impedance circuit Z and an output terminal out. The variablegain radio frequency amplifier (AMP) 1205 amplifiers a signal generatedby the impedance circuit Z. The gain is adjusted with a gain controlsignal (for example, an applied voltage) received from a gain adjustmentterminal 1206.

[0220] Next, with reference to FIG. 26, a PA-IC chip of which a poweramplifier (PA) 151 is structured as an IC chip will be described.Referring to FIG. 26, a power amplifier (PA) 151, a sensing means 1201,and an output power detecting means 1202 shown in FIG. 17 are structuredas the PA-IC chip.

[0221] In the PA-IC chip 1200, a signal proportional to a power to bedetected is obtained from a terminal d1. The signal is sent to a powercontrolling circuit (CONT) 171 shown in FIG. 11.

[0222] With the PA-IC chip 1200 having the sensing means 1201 and theoutput power detecting means 1202, a power can be sensed and detected.Thus, the size of the transmitting portion can be decreased.

[0223] Next, with reference to FIG. 27, a T/R switch IC chip of which aT/R switch is structured as an IC chip will be described. Referring toFIG. 27, a T/R switch circuit, a sensing means 1201, and an output powerdetecting means 1202 are structured as the T/R switch IC chip.

[0224] In this case, a signal proportional to an output power isobtained from a terminal d1 as with the above-described example. Thestructure of the sensing means 1201 is the same as the structure of thesensing means shown in FIG. 19, 20, 21, 24, and 25. In this example, atleast one of the power amplifier PA and the T/R switch is structured asan IC chip.

[0225] With the T/R switch IC chip having the sensing means 1201 and theoutput power detecting means 1202, a power can be sensed and detected.Thus, the size of the transmitting portion can be decreased.

[0226] Since the sensing means and the detecting means shown in FIGS.18, 23, 26, and 27 can detect a power that leaks out to the power supplyor ground without need to connect them to an RF signal line, the powerloss of the directional coupler and so forth can be suppressed. Thus,the power consumption of the transmitting portion can be decreased.

[0227]FIG. 28 is a plan view showing an IC chip having a power sensingdevice and a power detector shown in FIGS. 19 and 20. FIG. 29 is asectional view taken along line A-A of FIG. 28.

[0228] As shown in FIGS. 28 and 29, in the IC chip, a metal wire pattern1402 as a first metal layer (inner layer) is formed in an insulationlayer 1404. In addition, a metal wire pattern 1401 as a second metallayer (surface layer) is formed on the front surface of the insulationlayer 1404. The metal wire pattern 1401 is a power wire pattern forsupplying a power to a power amplifier (PA) 151. The metal wire pattern1402 is bent in an L letter shape. The bent edge of the metal wirepattern 1402 is connected to an output power detecting means 1202.

[0229] In this case, since the metal wire pattern 1402 is disposed onthe power wire pattern 1402 through the insulation layer 1404, acapacitance component is formed. An output power detecting means 1202connected to the metal wire pattern 1402 detects the amount of variationof the capacitance as the amount of variation of the power.

[0230] When a power sensing means or a power detecting means is disposedas an IC chip, for suppressing the loss, a metal layer is sometimesformed on the power wire pattern 1401 through an insulation layer so asto form a capacitance component and thereby capacitance-couple the powerwire pattern 1401 and the metal layer.

[0231] However, in this embodiment, the metal wire pattern 1402 formedin the insulation layer 1404 below the power wire pattern 1401 is variedso as to capacitance-couple the power wire pattern 1401 and the metalwire pattern 1402.

[0232] Generally, a wire for supplying a power (namely, the power wirepattern 1401) is formed in the IC chip with as large area as possible.In addition, the area of the metal wire pattern 1402 formed in theinsulation layer 1404 is less restricted. Thus, since the area of thecapacitor composed of the first and second layers can be increased, apower leakage can be easily detected. This condition is convenient fordetecting the power. It should be noted that even if the first layer andthe second layer are reversely formed, the same effect can be obtained.As shown in FIG. 30, the coupling capacitance is varied by adjusting thewire pattern widths of the metal wire patterns 1402 and 1401 so that thewire pattern width of the metal wire pattern 1402 is narrower than thewire pattern width of the power wire pattern 1401. Alternatively, asshown in FIG. 31, the coupling capacitance is varied by adjusting thewire pattern widths of the metal wire patterns 1402 and 1401 so that thewire pattern width of the metal wire pattern 1402 is wider than the wirepattern width of the power wire pattern 1401. In addition, as shown inFIG. 33, the coupling capacitance is varied by changing the formingdirection of the metal wire pattern 1402 and thereby varying the overlaparea between the metal wire patterns 1402 and 1401.

[0233] Last, with reference to FIG. 34, an antenna of the portableradiotelephone apparatus (hereinafter referred to as portable radioapparatus) according to another embodiment of the present invention willbe described. FIG. 34 is a block diagram showing the structure of theportable radio apparatus according to the embodiment of the presentinvention.

[0234] Referring to FIG. 34, the portable radio apparatus comprises acasing 1500, a radio circuit 1501, a matching circuit 1502, acontrolling circuit 1503, an ampere meter 1504, a power supply circuit1505, a current measuring probe 1506, and a transmitting amplifier 1509.The radio circuit 1501 comprises frequency converters 157 and 158 and avariable attenuator 152 shown in FIG. 11. An antenna 101 extrudes fromthe casing 1500.

[0235] The power supply circuit 1505 supplies a power to the radiocircuit 1501, the transmitting amplifier 1509, and the controllingcircuit 1503. The radio circuit 1501 modulates a supplied power andgenerates information signal at a transmission frequency. Theinformation signal is sent to the transmitting amplifier 1509. Thetransmitting amplifier 1509 amplifies the received signal and sends theamplified signal to the antenna 101. The amplified signal is transmittedfrom the antenna 101. However, part of the transmitted signal is sentback to the transmitting amplifier 1509 as a reflected wave. Thus, thegain and efficiency of the transmitting amplifier 1509 fluctuate,thereby causing the current consumption to fluctuate. The fluctuation ofthe current consumption is measured by the ampere meter 1504. Themeasured current level is sent to the controlling circuit 1503.

[0236] As fluctuation situations of the transmitting amplifier 1509, theamount of current that flow in the transmitting amplifier 1509 increasesor decreases. For simplicity, in the following description, it issupposed that the amount of current simply fluctuates. The controllingcircuit 1503 receives a signal from the ampere meter 1504 andelectrically adjusts a variable portion of the matching circuit 1502corresponding to the signal. An example of the variable portion is avariable capacitance of such as a semiconductor switch or asemiconductor.

[0237] Next, experimental results of the characteristic of the antenna101 in the operation state of the portable radio apparatus will bedescribed.

[0238]FIG. 35 is a perspective view showing a radio apparatus modelcorresponding to the portable radio apparatus shown in FIG. 34. FIGS. 36to 38 are graphs showing measured results of the radio apparatus modelshown in FIG. 35.

[0239] Referring to FIG. 35, the radio apparatus model comprises acasing 1500, a speaker 1511, a microphone 1512, an antenna cover 1514,and a radio circuit 501. The speaker 1511, the microphone 1512, and theantenna cover 1514 are disposed on the casing 150. The radio circuit1501 has a transmitting amplifier 1509. A coil-shaped antenna (helicalantenna) 101 is disposed in the antenna cover 1514.

[0240] A power feeder is connected from an external constant voltagesource 1510 to the casing 1500 so as to supply a power to the radiocircuit 1501. A current consumed in the radio apparatus model wasmeasured with an ampere meter 1513 of the constant voltage source 1510.A matching circuit 1502 is simulated by directly varying parameters ofthe antenna 101. The operation frequency of the radio apparatus model isaround 2 GHz. The length of the casing 1500 is equal to one wavelength(λ). The width of the casing 1500 is around ¼ of one wave length.The thickness of the casing 1500 is around {fraction (1/20)} of one wavelength. The length of the antenna 101 is around {fraction (1/10)} of onewave length.

[0241]FIG. 36 is a graph showing the relation between the operationstates and the current consumption of the radio apparatus model. FIG. 37is a graph showing a reflection coefficient at an input edge of theantenna 101 in individual operation states. FIG. 38 is a graph showingthe relation between individual operation states and average power onhorizontal plane radiated from the radio apparatus model.

[0242]FIGS. 36 and 37 show that the reflection coefficient of theantenna 101 varies corresponding to the individual operation states ofthe radio apparatus model and that the current consumption of thetransmitting amplifier 1509 varies corresponding to the individualoperation states. FIG. 38 shows that the radiation power of the antenna101 decreases in the order of the standby state, the holding state, andthe communicating state. These phenomena represent that the antenna 101is a load of the transmitting amplifier 1509. In other words, when theload varies, the operation state of the power amplifier PA and so forthvaries. Thus, the current consumption increases. It is clear that thefluctuation of the load is caused by the body of the user.

[0243] Thereafter, the antenna parameters are optimized corresponding tothe current value. The current consumption increases in the order of thestandby state, the holding state, and the communicating state. Thus, todecrease the current consumption as in the standby state, antennaparameters should be properly changed. In this experiment, as an antennaparameter, the antenna length was varied. This is because when theantenna length is varied, the response frequency of the antenna 10 canbe varied. Experimental results show that when the antenna lengthdecreases, the current consumption decreases. In the state that theantenna shrinks, the radiation power increases by around 2 dB incomparison with the state that the antenna does not shrink. Thus,experimental results show that the deterioration of the characteristicsof the antenna 101 becomes small in the method according to the presentinvention.

[0244] In the experiment, the antenna length was adjusted.Alternatively, the characteristics of the matching circuit 1502 can bevaried. FIG. 39 shows a real structure of which the characteristics ofthe matching circuit 1502 are varied.

[0245] Referring to FIG. 39, the matching circuit 1502 comprises anantenna device 1521, a variable capacitor 1522, a capacitor 1523, aninductor 1524, a variable resistor 1525, a controlling power supply1526, a radio frequency source 1527, and a resistor 1528.

[0246] The length of the antenna device 1521 is shorter than ¼ of onewave length. The capacitor 1523 is a low pass capacitor for preventing acurrent of the controlling power supply 1526 from flowing to the radiofrequency source 1527. The inductor 1524 is a coil for preventing aradio frequency signal from flowing to the controlling circuit 1503. Thevariable resistor 1525 controls the voltage applied to the antennadevice 1521. The variable capacitor 1522 is a capacitance that takesplace in the matching circuit 1502.

[0247] In this case, when the value of the variable resistor 1525 isvaried, the value of the variable capacitor 1522 is varied. The increaseof the value of the variable capacitor 1522 is equivalent to theincrease of the length of the antenna device 1521, thereby decreasingthe resonance frequency. The decrease of the value of the variablecapacitance 1522 is equivalent to the decrease of the length of theantenna device 1521, thereby increasing the resonance frequency. Thus,when the response frequency of the antenna device 1521 is varied, thematching condition can be varied.

[0248] Consequently, according to the portable radio apparatus accordingto the embodiment of the present invention, when the body of the userapproaches the antenna, the characteristics of the antenna can beimproved.

[0249] According to the above-described embodiments, the currentconsumption of the portable radio apparatus can be decreased. Inaddition, the efficiency of the portable radio apparatus can beimproved. Moreover, a non-time varying DC offset and a time-varying DCoffset that cause an error ratio of the receiving portion to increasecan be removed. Furthermore, the size of the portable radio apparatuscan be decreased. In addition, a blank channel can be searched at highspeed.

[0250] As described above, according to the present invention, thereceiving portion of the radio apparatus detects the power of the systemband and the power of a desired wave and controls the currentconsumption corresponding to the detected results. Thus, the powerconsumption of the radio apparatus can be decreased. When the receivingportion has an AC coupling capacitor, the deterioration of the frequencycharacteristic is compensated with the characteristic of the capacitor.Consequently, a DC offset that deteriorates the error ratio of thereceived signal can be removed. In addition, since the power of areflected wave by a reflector is detected by the directional coupler andeach circuit portion that generates a DC offset is controlledcorresponding to the reflected power and the transmitted power, atime-varying DC offset can be removed.

[0251] Since the synthesizer portion widens the band of a loop filterfor searching a blank channel, it can search a blank channel at highspeed.

[0252] When the synthesizer portion detects many blank channels, itcauses the radio apparatus to operate in a low power consumption mode.Thus, the power consumption of the radio apparatus can be decreased.

[0253] With respect to the transmitting portion, since the power sensingmeans and the power detecting means are structured as an IC chip, thesize of the transmitting portion can be decreased. In addition, adirectional coupler that causes a transmission power loss can beomitted. Thus, the power consumption of the radio apparatus can bedecreased.

[0254] With respect to the antenna, the operating current of the poweramplifier is detected. The matching circuit of the antenna is variedcorresponding to the operating current. Thus, the deterioration of thecharacteristic of the antenna can be compensated in individual operationstates of the radio apparatus. Consequently, the power consumption ofthe radio apparatus can be decreased. In addition, the performance ofthe radio apparatus can be improved.

[0255] Although the present invention has been shown and described withrespect to a best mode embodiment thereof, it should be understood bythose skilled in the art that the foregoing and various other changes,omissions, and additions in the form and detail thereof may be madetherein without departing from the spirit and scope of the presentinvention.

What is claimed is:
 1. A radio apparatus, comprising: receiving meansfor receiving a radio signal in a system band used in a radio system;synthesizing means for sending at least all desired frequency signals inthe system band to said receiving means; blank channel detecting meansfor detecting a blank channel of the system band; and controlling meansfor widening a loop band width of a PLL (Phase Lock Loop) of saidsynthesizing means while said blank channel detecting means is detectinga blank channel.
 2. A radio apparatus for repeatedly transmitting andreceiving a predetermined number of slots with a plurality of radiofrequency signals available in a radio system band and datacommunication using a blank slot, comprising: a phase synchronizingcircuit having: a phase comparator for generating a voltagecorresponding to the phase difference between the phase of a referencesignal and the phase of a comparing frequency divided signal, and avoltage controlling oscillator for generating a frequency correspondingto a control voltage; a first loop filter for causing said phasesynchronizing circuit to perform a phase synchronizing operation atpredetermined speed; a second loop filter for causing said phasesynchronizing circuit to perform the phase synchronizing operation athigher speed than the predetermined speed; and a loop filter selectingmeans for connecting said first loop filter to said voltage controllingoscillator in the period of one of the slots that is used for acommunication and for connecting said second loop filter to said voltagecontrolling oscillator when the period of the slot is over.
 3. The radioapparatus as set forth in claim 2, wherein a blank channel is searchedwhile said loop filter selecting means is connecting said second loopfilter to said voltage controlling oscillator.
 4. A radio apparatus,comprising: receiving means for receiving a radio signal in a systemband used in a radio system; power detecting means for detecting a powerconsumed in a band that covers at least the system band; and controllingmeans for decreasing a current consumption of said receiving means whenthe amount of power detected by said power detecting means is equal toor less than a predetermined value.
 5. The radio apparatus as set forthin claim 4, wherein said controlling means obtains the differencebetween the amount of power detected by said power detecting means andthe amount of power detected in a band of a desired channel or the ratiothereof and compares the difference or ratio with a predetermined valueso as to control the current consumption of said receiving means.
 6. Theradio apparatus as set forth in claim 4, wherein said power detectingmeans detects the amount of overall power in a band that covers at leastthe system band and the amount of power of a band of a desired channel,subtracts the amount of power in the band of the desired channel fromthe amount of overall power, and subtracts thermal noise that takesplace in the system band from the subtracted value.
 7. The radioapparatus as set forth in claim 1, further comprising: power controllingmeans for causing at least one of currents consumed by a low noiseamplifier and a frequency converter disposed in said receiving meanswhen the number of detected channels is equal to or larger than apredetermined value.
 8. A radio apparatus having a frequency converter,a low frequency amplifying, and an analog/digital converter for directlyconverting the frequency of an RF signal received by an antenna into abaseband signal, comprising: reflection detecting means for detecting atleast one of a reflection coefficient of the antenna and a reflectionpower of the power amplifier when an RF signal is transmitted; andcontrolling means for controlling at least one of DC offsets of thefrequency converter, the low frequency amplifier, and the analog/digitalconverter corresponding to the antenna reflection coefficient or theantenna reflection power detected by said reflection detecting means. 9.The radio apparatus as set forth in claim 8, further comprising: storingmeans for storing a conversion value corresponding to a reflectioncoefficient or a reflection power detected by said reflection detectingmeans; and means for reading a conversion value corresponding to adetected value of a reflection coefficient or a reflection powerdetected by said reflection detecting means from said storing means andsubtracting or adding the conversion value from or and a value detectedby said analog/digital converter.
 10. A radio apparatus having afrequency converter, a low frequency amplifying, and an analog/digitalconverter for directly converting the frequency of an RF signal receivedby an antenna into a baseband signal, comprising: reflection detectingmeans for detecting at least one of a reflection coefficient of theantenna and a reflection power of the power amplifier when an RF signalis transmitted; storing means for storing the value of the reflectioncoefficient or reflection power detected by said reflection detectingmeans; and controlling means for controlling at least one of DC offsetsof the frequency converter, the low frequency amplifier, and theanalog/digital converter corresponding to the antenna reflectioncoefficient or the antenna reflection power stored in said storing meanswhen the RF signal is received.
 11. A radio apparatus fortandem-connecting structural elements that are at least a frequencyconverter, a filter, and analog/digital converter through respectivecapacitors and directly converting the frequency of an RF signalreceived from an antenna to a baseband signal, comprising: processingmeans for adding a digital signal with inverse characteristics offrequency characteristics of the capacitors to a digital signalconverted by the analog/digital converter.
 12. The radio apparatus asset forth in claim 11, wherein said processing means comprises: storingmeans for storing data of the frequency characteristics of thecapacitors; and means for generating the inverse characteristicscorresponding to the data of the frequency characteristics stored insaid storing means.
 13. The radio apparatus as set forth in claim 11,further comprising: measuring means for measuring AC coupling frequencycharacteristics of the capacitors among the structural elements; andcalculating means for calculating the inverse characteristics of thecapacitors corresponding to the frequency characteristics measured bysaid measuring means.
 14. A radio apparatus, comprising: a transmittingportion having a power amplifier for sending a radio signal to anantenna; a receiving portion for receiving a radio signal from theantenna; a transmission/reception switch for selecting one of saidtransmitting portion or said receiving portion; transmission powerdetecting means, connected or capacitance-coupled to a power supplyportion of the power amplifier of said transmitting portion, fordetecting a transmission power corresponding to a fluctuation of thepower supply portion, the fluctuation taking place when a radio signalis transmitted; and controlling means for determining a transmissionpower of the transmitting portion corresponding to a transmission powerdetected by said transmission power detecting means.
 15. The radioapparatus as set forth in claim 14, wherein said transmission powerdetecting means is sensing means for sensing the amount of fluctuationof the power of the power supply portion.
 16. The radio apparatus as setforth in claim 15, wherein said sensing means is one of a diode, acapacitor, and a resistor.
 17. The radio apparatus as set forth in claim14, wherein said transmission power detecting means comprises: sensingmeans for sensing the amount of fluctuation of the power of the powersupply portion; and frequency converting means for converting a signalsensed by said sending means into a low frequency signal.
 18. The radioapparatus as set forth in claim 17, wherein said sensing means is one ofa diode, a capacitor, and a resistor.
 19. The radio apparatus as setforth in claim 14, wherein one of an IC chip of the power amplifier oran IC chip of said transmission/reception switch has said transmissionpower detecting means.
 20. The radio apparatus as set forth in claim 19,wherein the transmission/reception switch is a single-pole-dual-throwcircuit, and wherein said transmission/reception detecting means detectsa leakage current of the single-pole-dual-throw circuit.
 21. The radioapparatus as set forth in claim 20, wherein a transmission power inputterminal is connected to a drain (source) terminal of a shunttransistor, a source (drain) terminal of the shunt transistor beingconnected to a first terminal of a two-terminal impedance circuitcomposed of a resistor, a capacitor, or an inductance, a second terminalof the two-terminal impedance circuit being connected to ground, acontrol signal being sent to a gate T terminal of the shunt transistor,a current corresponding to the leakage current being detected from thefirst terminal so as to detect a leakage current of thesingle-pole-dual-throw circuit.
 22. The radio apparatus as set forth inclaim 19, wherein one of the power amplifier or saidtransmission/reception switch is structured as an IC chip, and whereinsaid transmission power detecting means comprises: a first metal wirepattern formed in the IC chip mainly composed of an insulation layer;and a second metal wire pattern, formed on the first metal wire patternthrough the insulation layer, for supplying a power.
 23. The radioapparatus as set forth in claim 22, wherein the first metal wire patternin the IC chip is varied so as to designate capacitance for detectingthe power.
 24. A radio apparatus, comprising: a radio circuit forsending a signal to be transmitted to an antenna through a transmittingamplifier; a power supply circuit for sending a power to said radiocircuit and the transmitting amplifier through a feeder; an ampere meterconnected to the feeder; and antenna characteristic varying means forvarying a matching characteristic of the antenna corresponding to acurrent value detected by said ampere meter.